The aim of the proposed work was to develop stable mucoadhesive in situ (Phenylepherine HCL) thermo-reversible nasal gel by cold technique and evaluated its efficacy against congestion due to allergic rhinitis. By means of hit and trial methodology screened formulations were prepare via numerous thermo-sensitive hydro-Gel (Pluronic F-127, Poloxamer 407) and muco-adhesives (Carbopol 934-P, Polyvinylpyrrolidone K-30, Hydroxy propyl methyl cellulose (HPMC), Sodium alginate and methylcellulose) and characterized. Out of 15 formulations; T1, T5, T7, T12 & T14 formulation compositions were selected on the basis of drug released (in-vitro or ex-vivo release found approx. up-to 97.8%) behavior, gelation and mucoadhesive strength. Resulted, drug transformed (crystalline to amorphous) form in gel state was indicated better drug absorption due to its improved physicochemical parameters. Additionally, optimized formulation (T1) histopathology and stability studied has been demonstrated none nasal mucosa damage and stable at storage conditions according to the ICH guidelines respectively. Therefore, the developed optimized thermo-reversible in-situ nasal (T1) gel was showed tremendous local safety action which can be considered to use for allergic nasal congestion and explore, further.